Pros:It is rare to find the best quality at an inexpensive price.
Cons:HMMMM - I guess if they were free it would be better.
The Bottom Line: Buy em.
As usual in my quest for the perfect product, I purchased every other headphone before I purchased the Koss headphones because I just thought that there is no way a $50 headphone will be as good as the $200 Shure ear buds or the Sennheiser (sp). Boy was I wrong. The base response is superb. Really, the only better sounding earphone if you could call it "portable" is the Bose Noise Cancelling headphones (which I also own). If you want to bike ride, you want to hear what is going on around you, but still have great bass. The Porta Pro's will deliver - the Bose can't.
But let me tell you the real story of why Koss is the only manufacturer to purchase from. My wife and I both have the Porta Pros. My wife was rollerblading with her Porta Pros and ran into a river (it had flooded onto the path under a bridge and she could not see it). The headphones got wet. The headphones started to crackle. I emailed Koss, who responded within 24 hours (unusual by today's standards), and they said "we have a no questions asked warranty" send six bucks, and we will repair them or replace them. IF FOR NO OTHER REASON, THIS IS WHY YOU SHOULD SUPPORT A GREAT COMPANY LIKE KOSS. I also ordered the SportaPro, they are only $30 bucks, and they say they spec out just like the Porta Pros - we will see.
The Porta Pros are easy to wear, because the headpiece is completely adjustable, they do not fatigue you like some headphones can. They are lightweight, and fold up compactly. For me, I hate the ear buds. They are hard plastic in my ear, and really have no bass response.